LS DR10: Morphological classification, "DUP", for radio galaxies?

Question

Hi there,

I have completed a cross-match of my sample of the brightest radio-sources in the southern sky (the G4Jy Sample) with LS DR10 ("tractor south") and have come across 59 sources with the morphological classification, "DUP". From reading this bit (https://www.legacysurvey.org/dr10/description/#morphological-classification):

"The sixth morphological type is "DUP," which is set for Gaia sources that are coincident with, and so have been fit by, an extended source. No optical flux is assigned to "DUP" sources, but they are retained to ensure that all Gaia sources appear in the catalogs even if Tractor preferred and fit a different source based on the deeper Legacy Surveys imaging."

I gather that "DUP" is effectively short-hand for "Duplicate"? If there is coincidence with Gaia, then these are likely quasars, yes? (I'll take a look with how this intersects with the proper-motion parameters, pmra and pmdec, in case any stars have crept into my catalogue.)

Kind regards,

Sarah

Answer 1

Hi Sarah.

Thank you for reaching out.
I asked the Tractor's Master Jedi, Dustin Lang, and he replied this:

Yes, DUP is short for Duplicate, and it should mean that whenever there is a DUP entry, there should be very nearby a galaxy source (TYPE = "REX" or "EXP" or "DEV" or "SER"), and that galaxy is the real thing you should look for.

Basically, we wanted our catalogs to have the property that *all* Gaia sources appear in our catalogs -- but these DUP ones are cases where there is a Gaia source for a galaxy -- eg, here's a DUP in DR9 --

https://www.legacysurvey.org/viewer/?ra=0.12864046205304328&dec=-1.2130245845128376&zoom=16&gaia-edr3

so these DUPs say "yes, there's a Gaia catalog entry here, but that's not *really* what we think is there".

Let us know if this clarifies your doubts about that. He also mentioned you two have an email exchange on a different topic. 

If any of your other tickets filed here have been addressed or solved there, would you please make a note about that on the tickets?

Thank you!
David

Comments

Hiya David,

Yes, that clarifies matters -- many thanks!

And don't worry, the emails were about other things :)

Thanks,
Sarah